The present invention concerns the evacuation of pipelines and particularly but not exclusively to the cleaning of pipelines by removal of material from therewithin.
Pipelines are used to convey fluid materials in many industrial environments. The production of many liquid products especially on an industrial scale, including chemicals, foodstuffs, beverages, pharmaceuticals, oils, cosmetics to name but a few, involves conveying product and/or substrate/ingredients for the product along pipelines.
Often it is required to clean the inside of such pipelines or at least to remove most of the material from therewithin. Cleaning is important for example when a different material is to be conveyed through a pipeline and contamination must be avoided. In many situations it is imperative that the pipeline is emptied completely of one material before another material can be conveyed therealong. It is also often desirable to recover material remaining in a pipeline, for example after a production run, to mitigate problems of wastage. The term xe2x80x9cevacuatedxe2x80x9d is used in this specification to refer to the removal of material from a pipeline, and particularly to the removal of all or substantially all product from a pipeline or section of pipeline.
One known method of evacuating pipelines is to force a device, often termed xe2x80x9ca pigxe2x80x9d through the pipeline under pressure from a propellant liquid or gas. Known pigs push material along a pipeline and out through a designated outlet in the pipeline, in many instances for collection for use or disposal. However, known designs of pig comprise a quite rigid and hard body. This means that the pig has to be diametrically significantly smaller than the inside diameter of a pipeline for it to be able to move around bends in the pipeline during use. Therefore with such known designs of pig, material is often left lining the inside of a pipeline thereby providing incomplete and often unsatisfactory evacuation of material.
It is therefore an object of the present invention to obviate or mitigate the aforesaid disadvantage of the prior art.
According to the present invention there is provided a pipeline evacuating device comprising a first relatively rigid portion and a second relatively deformable portion arranged to be compressable against the rigid portion when the device is forced through a pipeline containing material to be removed by the reaction of the material in the pipeline against the force of movement of the device, the compression causing the second portion to deform to at least substantially slidingly seal against the inside of the pipeline whereby to provide efficient evacuation of material from the pipeline as the device is forced therealong.
Preferably the second portion is resiliently deformable such that upon removal from pressurized conditions the pig returns to a non-compressed, relaxed condition. Preferably the second portion is arranged to be compressable to increase the relaxed width of the second portion in a direction generally perpendicular to the intended direction of movement of the device in use along a pipeline. Preferably the second portion is deformable desirably generally symmetrically, to form a seal, desirably in the form of a sealing collar, around the device to provide for substantially complete slidable sealing around the device in a pipeline. Preferably the force(s) exerted onto the pipeline by the second portion is/are greater than those exerted by the first portion. Preferably the second portion extends substantially across the width of the first portion, to provide for a sealing collar generally at one end of the first portion. Preferably the second, deformable portion is located on the one end which in use leads the device to provide for compression of the second portion between the fluid in the pipeline to be removed and the first rigid portion.
Preferably the device is generally elongate, and operable in the longitudinal direction. The device may taper at said one leading end but desirably comprises a surface generally perpendicular to the direction of movement of the device on which the reactive forces of the material act in use.
Preferably the first rigid portion is magnetic and/or magnetizable to facilitate detection of the location of the device in a pipeline. The rigid portion may comprise the same or similar material, desirably plastics material, as the second deformable portion, and with magnetic or magnetizable additive(s) therein which additive(s) may contribute to the relative rigidity of the first portion. The additive(s) may be metallic or metal compounds perhaps in powder and/or granular form. The first portion may be of greater diameter than the second portion when the device is in the relaxed condition.
Preferably the second portion is firmly attached to the first relatively rigid portion, and may be fused, and/or chemically bonded, thereto.
The first and second portions may be encased in a flexible outer sheath which sheath is preferably relative tough to provide protection of the first and second portions.
The device may comprise a further deformable portion which further portion is desirably arranged to be compressable along with the said deformable portion to provide a second slidable seal. Preferably the further second portion is provided at the other, rear end of the device to be deformable through compression between the means providing the force for movement of the device and the relatively rigid portion. Preferably the further second portion is similar to the said first second portion. The device may be generally symmetrical and preferably bidirectionally operable.
According to a further aspect of the present invention there is provided a method of evacuating material, such as fluid from a pipeline, the method comprising driving an evacuating device substantially as described in any of the preceding seven paragraphs down a pipeline containing material to be removed, the driving force being sufficient to cause the second, deformable portion of the device to be compressed between said driving force and the reactive force of the material in the pipeline to deform to form a substantially sliding seal on the inside of the pipeline and move the device along the pipeline to force fluid before the device along the pipeline for removal.
The driving force may be provided by pressurised air supplied into the pipeline behind the device. Alternatively or additionally the driving force may be provided by pressurised liquid, such as a cleaning liquid.
According to a still further aspect of the present invention there is provided a method of manufacture of a pipeline evacuating device substantially as hereinbefore described, the method comprising moulding a first rigid portion adjacent a second relatively deformable portion, curing the portions together, encasing the portions in a protective sheath and curing the sheath on the portions.
Curing may be effected by heat treatment. Magnetic and/or magnetizable additive(s) may be added to the first portion when in a pre-moulded liquid state, which additive(s) at least contribute to the relative rigidity of the first portion.